1. Field of the Invention The present invention relates to an image-forming apparatus such as a laser printer.
2. Description of the Related Art
Image-forming apparatuss such as laser printers well known in the art have been conventionally provided with a process cartridge that is detachably mounted in the image-forming apparatus, wherein the process cartridge further includes a drum cartridge and a developer cartridge that is detachably mounted on the drum cartridge.
The drum cartridge includes a photosensitive drum on the surface of which electrostatic latent images are formed based on prescribed image data. The developer cartridge includes a developing roller for developing the latent image formed on the photosensitive drum into a toner image. When the developer cartridge is mounted on the drum cartridge, the developing roller contacts the photosensitive drum. During image formation, the developing roller is driven to rotate in a direction opposite that of the photosensitive drum. Specifically, when the latent image formed on the surface of the photosensitive drum rotates opposite the developing roller, toner carried on the developing roller is supplied to the latent image, developing the image into a toner image. Subsequently, the toner image is rotated opposite a transfer roller also disposed in opposition to the photosensitive drum. At this time, the toner image carried on the photosensitive drum is transferred onto a sheet of paper conveyed between the photosensitive drum and the transfer roller.
One such image-forming apparatus including a process cartridge with this construction is disclosed in Japanese Patent Application Publication No. 2003-84645. This image-forming apparatus enables the developer cartridge and drum cartridge to be mounted in or removed from the main body of the image-forming apparatus as a unit. Alternatively, the developer cartridge may also be removed alone from the main body, while the drum cartridge remains therein.
When the developer cartridge in this conventional image-forming apparatus runs out of toner before the drum cartridge has reached the end of its life, the user removes only the developer cartridge from the main body and replaces this cartridge with a new developer cartridge. However, since the developer cartridge in this conventional construction can be removed from the image-forming apparatus as a with the drum cartridge, when replacing the developer cartridge with a new cartridge, the user may mistakenly replace both the developer cartridge and the drum cartridge together and discard the older drum cartridge, even though this drum cartridge has not reached the end of its life.